Petrochemical processes

ABSTRACT

Petrochemical processes, including reforming processes are described herein. The reforming processes generally include introducing an input stream to a reforming unit having a reforming catalyst disposed therein, wherein the input stream includes a naphtha having an N+2A value of from about 65 to about 85 and contacting the input stream with the reforming catalyst and hydrogen to form an output stream.

FIELD

Embodiments of the present invention generally relate to petrochemicalprocesses, such as reforming processes. In particular, embodiments ofthe invention relate to feedstocks for reforming processes.

BACKGROUND

Reforming processes generally include supplying straight run feedstocks,such as naphtha, to the reformer to form output streams having anincreased octane number. However, the final octane number of the outputstream, such as the octane number of gasoline and the value thereof, aredetermined by the N+2A value of the input stream.

Therefore, a need exists to provide a process of increasing the finaloctane number of reformer output streams.

SUMMARY

Embodiments of the present invention include reforming processes. Thereforming processes generally include introducing an input stream to areforming unit having a reforming catalyst disposed therein, wherein theinput stream includes a naphtha having an N+2A of from about 65 to about85 and contacting the input stream with the reforming catalyst andhydrogen to form an output stream.

Another embodiment generally includes a petrochemical process. Thepetrochemical process generally includes introducing a first inputstream to a cracking unit, wherein the first input stream includes anaphtha feedstock, cracking the naphtha feedstock within the crackingunit to form a first output stream including light olefins and pygas,passing the pygas from the cracking unit to an extraction unit andseparating benzene and toluene from the pygas within the extractionunit. The process further includes recovering a raffmate from theextraction unit, passing the raffinate from the extraction unit to areforming unit having a reforming catalyst disposed therein, contactingthe raffmate with the reforming catalyst to form a second output streamand recovering the second output stream from the reforming unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a conventional reforming process.

FIG. 2 illustrates a portion of a petrochemical process.

DETAILED DESCRIPTION

Introduction and Definitions

A detailed description will now be provided. Each of the appended claimsdefines a separate invention, which for infringement purposes isrecognized as including equivalents to the various elements orlimitations specified in the claims. Depending on the context, allreferences below to the “invention” may in some cases refer to certainspecific embodiments only. In other cases it will be recognized thatreferences to the “invention” will refer to subject matter recited inone or more, but not necessarily all, of the claims. Each of theinventions will now be described in greater detail below, includingspecific embodiments, versions and examples, but the inventions are notlimited to these embodiments, versions or examples, which are includedto enable a person having ordinary skill in the art to make and use theinventions when the information in this patent is combined withavailable information and technology.

Various terms as used herein are shown below. To the extent a term usedin a claim is not defined below, it should be given the broadestdefinition persons in the pertinent art have given that term asreflected in printed publications and issued patents. Further, unlessotherwise specified, all compounds described herein may be substitutedor unsubstituted and the listing of compounds includes derivativesthereof.

Although not shown herein, the process stream flow may be modified basedon unit optimization so long as the modification complies with thespirit of the invention, as defined by the claims. For example, at leasta portion of any overhead fraction may be recycled as input to any othersystem within the process. Also, additional process equipment, such asheat exchangers, may be employed throughout the processes describedherein and such placement is generally known to one skilled in the art.

Further, while described below in terms of primary components, thestreams indicated below may include any additional components as knownto one skilled in the art.

The term “regeneration” refers to a process for renewing catalystactivity and/or making a catalyst reusable after its activity hasreached an unacceptable/inefficient level. Examples of such regenerationmay include passing steam over a catalyst bed or burning off carbonresidue, for example.

As used herein, the term “naphtha” refers to a cut in the range of C₅ toabout 420° F. The term light virgin naphtha refers a naphtha cut in therange of C₅ to about 160° F., intermediate virgin naphtha refers to anaphtha cut in the range of from about 160° F. to about 280° F. andheavy virgin naphtha refers to a naphtha cut in the range of from about280° F. to about 380° F. The term “virgin” refers to petroleum oilswhich have not been cracked or otherwise subjected to any treatmentwhich would produce appreciable chemical change in their components.

The term “cut” refers to that portion of crude oil boiling withincertain temperature limits. The limits may be on a crude assay trueboiling point basis, for example.

The term “reforming” refers to the conversion of naphtha fractions toproducts of higher octane value.

The term “research octane number” refers to the percentage by volume ofisooctane in a blend of isooctane and n-heptane that knocks with thesame intensity as the fuel being tested.

The term “straight run feedstock” refers to an uncracked feedstock. Theterm “straight run gasoline” refers to an uncracked gasoline fractiondistilled from crude oil.

FIG. 1 illustrates a conventional reforming process 100. The reformingprocess 100 generally includes providing an input stream 102 to areformer unit 104 to form an output stream 106. Although illustrated inFIG. 1 as a single reformer unit 104, it is known in the art that thereforming process 100 may include a plurality of individual reformerunits/stages.

The input stream 102 generally includes any hydrocarbon feedstock havinga boiling point within the gasoline range. For example, the hydrocarbonfeedstock may include light hydrocarbon oils boiling from about 70° F.to about 500° F. or from about 180° F. to about 400° F., for example.

Generally, the input stream 102 includes compounds selected from heavystraight run gasolines and heavy straight run naphthas (heavy virginnaphtha).

In addition, hydrogen is fed to the unit in any manner known to oneskilled in the art. For example, hydrogen may be fed to and combinedwith the input stream 102 (e.g., input stream 102 includes hydrogen).The hydrogen may be added at a rate of from about 1,000 to about 8,000scf/bbbl of input stream 102, for example.

The reformer unit 104 may include any vessel or number of vessels knownto one skilled in the art, such as a fixed bed reaction vessel, forexample. The reformer unit 104 may be operated at a reactor pressure offrom about 30 psig to about 1000 psig or from about 30 psig to about1000 psig, for example, a weight hourly space velocity (WHSV) of fromabout 0.5/hour to about 20/hour or from about 1/hour to about 10/hourand a hydrogen to input ratio of from about 1 to about 10 moles ofhydrogen per mole of feed, for example.

The reformer unit 104 generally includes a reforming catalyst disposedtherein. The reforming catalyst generally includes a metal component.The metal component may include a Group VIII noble metal, such asplatinum.

The reforming catalyst may be supported or unsupported. When supported,the support material may include a refractory oxide (e.g., clay,alumina, silica or combinations thereof) or a zeolite, for example. Thezeolite support may have an effective pore diameter of from about 6angstroms to about 15 angstroms (e.g., zeolite-X, zeolite Y orzeolite-L), for example.

The reforming catalyst may further include a promoter. The promoter mayinclude a metal selected from Groups IIA, IVA, IB, VIB, BIIB and BIII,such as gallium, tin, copper, chromium, rhenium, iridium andcombinations thereof. The promoter may be present in an amount of fromabout 0.01 wt. % to about 5 wt. % or from about 0.1 wt. % to about 3 wt.% or from about 0.2 wt. % to 3 wt. %, for example.

Certain compounds present in either the input stream 102 or producedduring the reaction, such as certain metals, hydrogen sulfide, ammonia,organic nitrogen and sulfur compounds, may deactivate the catalyst.Therefore, the reforming process 100 may further include a feedpretreater (not shown,) such as a hydrotreater to reduce the amount ofthese compounds present in the input stream 102.

However, reforming catalysts generally still experience deactivation.Therefore, the reforming process 100 may be continuous (e.g., on-linecatalyst regeneration), cyclic (e.g., swing reactors) orsemi-regenerative (e.g., off-line regeneration) depending upon thefrequency of catalyst regeneration and other process considerations, forexample.

Catalyst regeneration may include high temperature oxidation followed bychlorination, for example. See, U.S. Pat. No. 4,595,668, U.S. Pat. No.4,645,586, U.S. Pat. No. 4,636,298, U.S. Pat. No. 4,594,145 and U.S.Pat. No. 4,104,320.

The input stream 102 generally contacts the reforming catalyst withinthe reformer unit 104 to form the output stream 106. The heavy straightrun naphthas of the input stream 102 may have an N+2A value(naphthenes+2×aromatics) content of from about 30 to about 60 or fromabout 40 to about 55, for example. In addition, the output stream 106generally includes a compound having an increased octane number than theinput stream 102. However, the octane number is generally dependent uponthe product produced and the intended use thereof.

The N+2A value of the input stream 102 generally provides limits on theoctane number on the products within the output stream 106. For example,a higher N+2A value generally results in an increased C₅ and greateryield in the output stream 106. In addition, a higher N+2A value resultsin an increased ability to boost the octane number of the output and anincreased liquid yield in the output stream 106, for example.

FIG. 2 illustrates a portion of a petrochemical process 200. The process200 generally includes providing an input stream 202 to a naphthacracker 204 to form an overhead fraction 206.

The input stream 202 generally includes a naphtha feedstock. The naphthafeedstock may include a mixture of paraffinic, naphthenic and aromatichydrocarbons having varied molecular weight and molecular structure, forexample.

In one embodiment, the input stream 202 includes virgin naphtha. Thevirgin naphtha may be supplied from any source. However, in oneembodiment, the virgin naphtha is supplied from a former reformer feedsource. For example, embodiments of the invention may includeretrofitting an existing petrochemical process including a reformingunit, such as that illustrated in FIG. 1. Such retrofit may includererouting the feed from the reforming unit to the naphtha cracker, forexample. The aromatics content of the former reforming feed (N+2A offrom about 40 to about 50) is contemplated to result in an increasedconversion rate. The N+2A value of the former reforming feed may furtherprovide more cracking feed to the naphtha cracker due to the higherparaffin level, for example.

The naphtha cracker 204 may include any vessel or number of vesselsknown to one skilled in the art for the production of light olefins,such as ethylene and/or propylene, for example. In one embodiment, thenaphtha cracker 204 includes a steam cracker.

The overhead fraction 206 generally includes light olefins (e.g.,ethylene and propylene.)

In addition to the overhead fraction 206, the naphtha cracking processgenerally produces pyrolysis gasoline as a by-product, which isrecovered via line 208.

Pyrolysis gasoline (also referred to as “pygas”) is a liquid by-productof the cracking process and is generally a gasoline (e.g., a highlyunsaturated hydrocarbon mixture (C₅ to C₁₄) that is rich in dienes,olefin and aromatics) boiling in the temperature range of from about 97°F. to about 450° F., for example.

The pygas may be sent to an extraction unit 210 to separate benzeneand/or toluene from other components present in the pyrolysis gasoline,for example. Although not shown in the figures, it is known to oneskilled in the art that the pygas may undergo hydrogenation prior toextraction, for example. Such extraction processes are generally knownto one skilled in the art. See, U.S. Pat. No. 3,714,033.

A BTX fraction may be recovered via line 212. The BTX fraction mayinclude benzene, toluene, C₈ aromatics (ortho-xylene, meta-xylene,paraxylene and ethyl benzene), C₉ aromatics and combinations thereof,for example.

Raffmate may be recovered via line 214. The term “raffinate” refers tothe residue recovered from an extraction process. Embodiments of theinvention generally include utilizing the raffnate formed from suchextraction as input for reforming units. It is contemplated that theraffinate aromatics content (N+2A of from about 75 to about 85) wouldresult in more efficient boosting of the octane number of the reforminginput stream. Therefore, embodiments of the invention generally includepassing the raffmate via line 214 to a reformer unit 216 to form areformer output 218.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof and the scope thereof isdetermined by the claims that follow.

1. A reforming process comprising: introducing an input stream to areforming unit comprising a reforming catalyst disposed therein, whereinthe input stream comprises a naphtha comprising a N+2A value of fromabout 65 to about 85; and contacting the input stream with the reformingcatalyst and hydrogen to form an output stream.
 2. The process of claim1, wherein the napththa is supplied from naphtha cracking raffmate. 3.The process of claim 2, wherein the naphtha cracking raffinate comprisesa N+2A value of from about 75 to about
 85. 4. The process of claim 1,wherein the output stream comprises a naphtha having an output researchoctane number that is higher than an input research octane number of theinput stream.
 5. The process of claim 1, wherein the reforming catalystcomprises a Group VIII noble metal.
 6. The process of claim 5, whereinthe reforming catalyst comprises platinum.
 7. The process of claim 1,wherein the reforming catalyst comprises a promoter selected fromgallium, tin, copper, chromium, rhenium, iridium and combinationsthereof.
 8. The process of claim 7, wherein the reforming catalystcomprises from about 0.01 wt. % to about 5 wt. % promoter.
 9. Theprocess of claim 1 further comprising supplying hydrogen to thereforming unit.
 10. The process of claim 9, wherein the hydrogen issupplied at a rate of from about 1 mole of hydrogen/mole of input streamto about 10 moles of hydrogen/mole of input stream.
 11. The process ofclaim 1, wherein the reforming unit comprises a weight hourly spacevelocity of from about 0.5/hour to about 20/hour.
 12. A petrochemicalprocess comprising: introducing a first input stream to a cracking unit,wherein the first input stream comprises a naphtha feedstock; crackingthe naphtha feedstock within the cracking unit to form a first outputstream comprising light olefins and pygas; passing the pygas from thecracking unit to an extraction unit; separating benzene and toluene fromthe pygas within the extraction unit; recovering a raffinate from theextraction unit; passing the raffinate from the extraction unit to areforming unit having a reforming catalyst disposed therein; contactingthe raffmate with the reforming catalyst to form a second output stream;and recovering the second output stream from the reforming unit.
 13. Theprocess of claim 12, wherein the napththa feedstock comprises straightrun naphtha.
 14. The process of claim 13, wherein the straight runnaphtha comprises a N+2A value of from about 40 to about
 55. 15. Theprocess of claim 12, wherein the cracking unit comprises a steamcracker.
 16. The process of claim 12 further comprising hydrogenatingthe pygas prior to extraction.
 17. The process of claim 12, wherein theraffmate comprises a N+2A value of from about 75 to about
 85. 18. Theprocess of claim 12, wherein the reforming catalyst comprises a GroupVIII noble metal.
 19. The process of claim 12, wherein the reformingcatalyst comprises a promoter selected from gallium, tin, copper,chromium, rhenium, iridium and combinations thereof
 20. The process ofclaim 12 further comprising supplying hydrogen to the reforming unit.